Cable-type secondary battery

ABSTRACT

The present invention relates to a cable-type secondary battery having a horizontal cross section of a predetermined shape and extending longitudinally, comprising: a core for supplying lithium ions; an inner electrode, comprising a spiral electrode formed by spirally twisting two or more wire-type inner current collectors coated with an inner electrode active material on the surface thereof; a separation layer surrounding the outer surface of the inner electrode to prevent a short circuit between electrodes; and an outer electrode surrounding the outer surface of the separation layer, and comprising an outer electrode active material layer and an outer current collector. 
     The core for supplying lithium ions is disposed in the inner electrode, from which the electrolyte of the core for supplying lithium ions can be easily penetrated into an electrode active material, thereby facilitating the supply and exchange of lithium ions.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of International Application No.PCT/KR2012/008401 filed on Oct. 15, 2012, which claims priority under 35USC 119(a) to Korean Patent Application No. 10-2011-0104875 filed in theRepublic of Korea on Oct. 13, 2011 and Korean Patent Application No.10-2012-0114117 filed in the Republic of Korea on Oct. 15, 2012, thedisclosures thereof are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a cable-type secondary battery, whichcan freely change in shape, and more particularly to a cable-typesecondary battery having a core for supplying lithium ions.

BACKGROUND ART

Secondary batteries are devices capable of storing energy in chemicalform and of converting into electrical energy to generate electricitywhen needed. The secondary batteries are also referred to asrechargeable batteries because they can be recharged repeatedly. Commonsecondary batteries include lead accumulators, NiCd batteries, NiMHaccumulators, Li-ion batteries, Li-ion polymer batteries, and the like.When compared with disposable primary batteries, not only are thesecondary batteries more economically efficient, they are also moreenvironmentally friendly.

Secondary batteries are currently used in applications requiring lowelectric power, for example, equipment to start vehicles, mobiledevices, tools, uninterruptible power supplies, and the like. Recently,as the development of wireless communication technologies has beenleading to the popularization of mobile devices and even to themobilization of many kinds of conventional devices, the demand forsecondary batteries has been dramatically increasing. Secondarybatteries are also used in environmentally friendly next-generationvehicles such as hybrid vehicles and electric vehicles to reduce thecosts and weight and to increase the service life of the vehicles.

Generally, secondary batteries have a cylindrical, prismatic, or pouchshape. This is associated with a fabrication process of the secondarybatteries in which an electrode assembly composed of an anode, acathode, and a separator is mounted in a cylindrical or prismatic metalcasing or a pouch-shaped casing of an aluminum laminate sheet, and inwhich the casing is filled with electrolyte. Because a predeterminedmounting space for the electrode assembly is necessary in this process,the cylindrical, prismatic or pouch shape of the secondary batteries isa limitation in developing various shapes of mobile devices.Accordingly, there is a need for secondary batteries of a new structurethat are easily adaptable in shape.

To fulfill this need, suggestions have been made to develop linearbatteries having a very high ratio of length to cross-sectionaldiameter. Korean Patent Application publication No. 2005-99903 disclosesa flexible battery consisting of an inner electrode, an outer electrodeand an electrolyte layer interposed therebetween. However, such batteryhas insufficient flexibility. The linear batteries use a polymerelectrolyte to form an electrolyte layer, but this causes difficultiesin the inflow of the electrolyte into an electrode active material,thereby increasing the resistance of the batteries and deteriorating thecapacity and cycle characteristics thereof.

DISCLOSURE Technical Problem

The present invention is designed to solve the problems of the priorart, and therefore it is an object of the present invention to provide asecondary battery having a new linear structure, which can easily changein shape, maintain excellent stability and performances as a secondarybattery, and facilitate the inflow of an electrolyte into an electrodeactive material.

Technical Solution

In order to achieve the objects, the present invention provides acable-type secondary battery having a horizontal cross section of apredetermined shape and extending longitudinally, comprising: a core forsupplying lithium ions, which comprises an electrolyte; an innerelectrode, comprising a spiral electrode formed by spirally twisting twoor more wire-type inner current collectors coated with an innerelectrode active material on the surface thereof; a separation layersurrounding the outer surface of the inner electrode to prevent a shortcircuit between electrodes; and an outer electrode surrounding the outersurface of the separation layer, and comprising an outer electrodeactive material layer and an outer current collector.

In the inner electrode of the present invention, one or more spiralelectrodes may be wound to surround the outer surface of the core forsupplying lithium ions, or one or more spiral electrodes may be arrangedparallel to each other in the longitudinal direction along the outersurface of the core for supplying lithium ions, but the form of theinner electrode is not limited thereto.

In the outer electrode, the outer electrode active material layer may beformed to surround the outer surface of the separation layer, and theouter current collector may be formed to surround the outer surface ofthe outer electrode active material layer; the outer current collectormay be formed to surround the outer surface of the separation layer, andthe outer electrode active material layer may be formed to surround theouter surface of the outer current collector; the outer currentcollector may be formed to surround the outer surface of the separationlayer, and the outer electrode active material layer may be formed tosurround the outer surface of the outer current collector and come intocontact with the separation layer; or the outer electrode activematerial layer may be formed to surround the outer surface of theseparation layer, and the outer current collector may be formed to beincluded inside the outer electrode active material layer by beingcovered therein and to surround the outer surface of the separationlayer with spacing apart therefrom.

In the present invention, the outer current collector is notparticularly limited to its forms, but is preferably in the form of apipe, a wound wire, a wound sheet or a mesh.

The inner current collector is not particularly limited to its kinds,but is made of stainless steel, aluminum, nickel, titanium, sinteredcarbon, or copper; stainless steel treated with carbon, nickel, titaniumor silver on the surface thereof; an aluminum-cadmium alloy; anon-conductive polymer treated with a conductive material on the surfacethereof; or a conductive polymer.

Examples of the conductive material which may be used in the presentinvention include polyacetylene, polyaniline, polypyrrole,polythiophene, polysulfurnitride, indium tin oxide (ITO), silver,palladium, nickel, and mixtures thereof. Examples of the conductivepolymer which may be used in the present invention includepolyacetylene, polyaniline, polypyrrole, polythiophene,polysulfurnitride, and mixtures thereof.

The outer current collector may be made of stainless steel, aluminum,nickel, titanium, sintered carbon, or copper; stainless steel treatedwith carbon, nickel, titanium or silver on the surface thereof; analuminum-cadmium alloy; a non-conductive polymer treated with aconductive material on the surface thereof; a conductive polymer; ametal paste comprising metal powders of Ni, Al, Au, Ag, Al, Pd/Ag, Cr,Ta, Cu, Ba or ITO; or a carbon paste comprising carbon powders ofgraphite, carbon black or carbon nanotube.

In the present invention, the core for supplying lithium ions comprisesan electrolyte, and examples of the electrolyte may include, but are notparticularly limited to, a non-aqueous electrolyte solution usingethylene carbonate (EC), propylene carbonate (PC), butylene carbonate(BC), vinylene carbonate (VC), diethyl carbonate (DEC), dimethylcarbonate (DMC), ethyl methyl carbonate (EMC), methyl formate (MF),γ-butyrolactone (γ-BL), sulfolane, methyl acetate (MA) or methylpropionate (MP); a gel polymer electrolyte using PEO, PVdF, PVdF-HEP,PMMA, PAN, or PVAc; and a solid electrolyte using PEO, polypropyleneoxide (PPO), polyether imine (PEI), polyethylene sulphide (PES), orpolyvinyl acetate (PVAc). The electrolyte further comprises a lithiumsalt, and the preferred examples of the lithium salt include LiCl, LiBr,LiI, LiClO₄, LiBF₄, LiB₁₀Cl₁₀, LiPF₆, LiCF₃SO₃, LiCF₃CO₂, LiAsF₆,LiSbF₆, LiAlCl₄, CH₃SO₃Li, CF₃SO₃Li, (CF₃SO₂)₂NLi, lithium chloroborate,lower aliphatic lithium carbonate, lithium tetraphenylborate, andmixtures thereof.

In the present invention, the inner electrode may be an anode and theouter electrode may be a cathode, or the inner electrode may be acathode and the outer electrode may be an anode.

When the inner electrode of the present invention is an anode and theouter electrode is a cathode, the inner electrode active material layermay comprise an active material selected from the group consisting ofnatural graphite, artificial graphite, or carbonaceous material;lithium-titanium complex oxide (LTO), and metals (Me) including Si, Sn,Li, Zn, Mg, Cd, Ce, Ni and Fe; alloys of the metals; oxides (MeOx) ofthe metals; complexes of the metals and carbon; and mixtures thereof,and the outer electrode active material layer may comprise an activematerial selected from the group consisting of LiCoO₂, LiNiO₂, LiMn₂O₄,LiCoPO₄, LiFePO₄, LiNiMnCoO₂, LiNi_(1-x-y-z)Co_(x)M1_(y)M2_(z)O₂(wherein M1 and M2 are each independently selected from the groupconsisting of Al, Ni, Co, Fe, Mn, V, Cr, Ti, W, Ta, Mg and Mo, and x, yand z are each independently an atomic fraction of oxide-formingelements, in which 0≦x<0.5, 0≦y<0.5, 0≦z<0.5, and x+y+z≦1), and mixturesthereof.

Alternatively, when the inner electrode is a cathode and the outerelectrode is an anode, the inner electrode active material layer maycomprise an active material selected from the group consisting ofLiCoO₂, LiNiO₂, LiMn₂O₄, LiCoPO₄, LiFePO₄, LiNiMnCoO₂,LiNi_(1-x-y-z)Co_(x)M1_(y)M2_(z)O₂ (wherein M1 and M2 are eachindependently selected from the group consisting of Al, Ni, Co, Fe, Mn,V, Cr, Ti, W, Ta, Mg and Mo, and x, y and z are each independently anatomic fraction of oxide-forming elements, in which 0≦x<0.5, 0≦y<0.5,0≦z<0.5, and x+y+z≦1), and mixtures thereof, and the outer electrodeactive material layer may comprise an active material selected from thegroup consisting of natural graphite, artificial graphite, orcarbonaceous material; lithium-titanium complex oxide (LTO), and metals(Me) including Si, Sn, Li, Zn, Mg, Cd, Ce, Ni and Fe; alloys of themetals; oxides (MeOx) of the metals; complexes of the metals and carbon;and mixtures thereof, but the present invention is not particularlylimited thereto. In the present invention, the separation layer may bean electrolyte layer or a separator.

The electrolyte layer is not particularly limited to its kinds, butpreferably is made of an electrolyte selected from a gel polymerelectrolyte using PEO, PVdF, PVdF-HFP, PMMA, PAN, or PVAc; and a solidelectrolyte of PEO, polypropylene oxide (PPO), polyether imine (PEI),polyethylene sulphide (PES), or polyvinyl acetate (PVAc). Also, theelectrolyte layer may further comprise a lithium salt, and non-limitingexamples of the lithium salt include LiCl, LiBr, LiI, LiClO₄, LiBF₄,LiB₁₀Cl₁₀, LiPF₆, LiCF₃SO₃, LiCF₃CO₂, LiAsF₆, LiSbF₆, LiAlCl₄, CH₃SO₃Li,CF₃SO₃Li, (CF₃SO₂)₂NLi, lithium chloroborate, lower aliphatic lithiumcarbonate, lithium tetraphenylborate, and mixtures thereof.

When the separation layer is a separator, the cable-type secondarybattery of the present invention needs an electrolyte solution, andexamples of the separator may include, but is not limited to, a poroussubstrate made of a polyolefin-based polymer selected from the groupconsisting of ethylene homopolymers, propylene homopolymers,ethylene-butene copolymers, ethylene-hexene copolymers, andethylene-methacrylate copolymers; a porous substrate made of a polymerselected from the group consisting of polyesters, polyacetals,polyamides, polycarbonates, polyimides, polyether ether ketones,polyether sulfones, polyphenylene oxides, polyphenylene sulfides andpolyethylene naphthalenes; or a porous substrate made of a mixture ofinorganic particles and a binder polymer.

Further, the present invention provides a cable-type secondary batteryhaving multiple inner electrodes.

Advantageous Effects

In accordance with the present invention, a core for supplying lithiumions, which comprises an electrolyte, is disposed in the inner electrodehaving an open structure and comprising a spiral electrode, from whichthe electrolyte of the core for supplying lithium ions can be easilypenetrated into an electrode active material, thereby facilitating thesupply and exchange of lithium ions. Accordingly, the cable-typesecondary battery of the present invention has such a core for supplyinglithium ions to exhibit good capacity and superior cyclecharacteristics.

Also, in the cable-type secondary battery of the present invention usinga spiral electrode as an inner electrode, such a spiral electrode canhave an active material layer having a thin thickness to facilitate thediffusion of lithium ions and eventually provide good batteryperformances, which results in an increased surface area for reactionwith lithium ions during a charging/discharging process to improve therate characteristic of the battery.

DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate preferred embodiments of thepresent invention and, together with the foregoing disclosure, serve toprovide further understanding of the technical spirit of the presentinvention. However, the present invention is not to be construed asbeing limited to the drawings.

FIG. 1 is a perspective view showing a cable-type secondary batteryhaving one wound spiral electrode as an inner electrode in accordancewith a preferred embodiment of the present invention.

FIG. 2 is a perspective view schematically showing a spiral electrodeaccording to a preferred embodiment of the present invention.

FIG. 3 is a cross-sectional view of FIG. 1.

FIG. 4 is a perspective view showing a cable-type secondary batteryhaving an inner electrode consisting of two wound spiral electrodes inaccordance with a preferred embodiment of the present invention.

FIG. 5 is a perspective view showing a cable-type secondary batteryhaving an inner electrode consisting of multiple spiral electrodesarranged parallel to each other in the longitudinal direction inaccordance with a preferred embodiment of the present invention.

FIG. 6 is a perspective view showing a cable-type secondary batteryhaving multiple inner electrodes in accordance with a preferredembodiment of the present invention.

BEST MODE

Hereinafter, the present invention will be described in detail withreference to the accompanying drawings. Prior to the description, itshould be understood that the terms used in the specification and theappended claims should not be construed as limited to general anddictionary meanings, but interpreted based on the meanings and conceptscorresponding to technical aspects of the present invention on the basisof the principle that the inventor is allowed to define termsappropriately for the best explanation.

FIG. 1 schematically shows a cable-type secondary battery according toone embodiment of the present invention. However, the configurationsillustrated in the drawings and the embodiments are just preferableexamples for the purpose of illustrations only, not intended to limitthe scope of the disclosure, so it should be understood that otherequivalents and modifications could be made thereto without departingfrom the spirit and scope of the disclosure.

Referring to FIG. 1, a cable-type secondary battery 100 has a horizontalcross section of a predetermined shape and extending longitudinally, andcomprises a core 110 for supplying lithium ions, which comprises anelectrolyte; an inner electrode 120 surrounding the outer surface of thecore 110 for supplying lithium ions, and comprising a spiral electrodeformed by spirally twisting two or more wire-type current collectorscoated with an inner electrode active material on the surface thereof; aseparation layer 130 surrounding the outer surface of the innerelectrode to prevent a short circuit between electrodes; and an outerelectrode surrounding the outer surface of the separation layer 130, andcomprising an outer electrode active material layer and an outer currentcollector.

In the present invention, the outer electrode may be formed in variousembodiments depending on the disposition of the outer electrode activematerial layer and the outer current collector, which come into contactwith the separation layer.

In FIG. 1, the outer electrode comprises an outer electrode activematerial layer 140 surrounding the outer surface of the separation layer130 and an outer current collector 150 surrounding the outer surface ofthe outer electrode active material layer 140.

Also, the outer electrode of the cable-type secondary battery accordingto one embodiment of the present invention may be formed in a structurehaving the outer current collector formed to surround the outer surfaceof the separation layer, and the outer electrode active material layerformed to surround the outer surface of the outer current collector; astructure having the outer current collector formed to surround theouter surface of the separation layer, and the outer electrode activematerial layer formed to surround the outer surface of the outer currentcollector and to come into contact with the separation layer; or astructure having the outer electrode active material layer formed tosurround the outer surface of the separation layer, and the outercurrent collector formed to be included inside the outer electrodeactive material layer by being covered therein and to surround the outersurface of the separation layer with spacing apart therefrom.

The term ‘a predetermined shape’ used herein is not particularly limitedto any shape, and refers to any shape that does not damage the nature ofthe present invention. The cable-type secondary battery of the presentinvention has a horizontal cross section of a predetermined shape, alinear structure, which extends in the longitudinal direction, andflexibility, so it can freely change in shape. Also, the inner electrodehaving a spiral electrode is in the form of an open structure, and theterm ‘open structure’ used herein means that a structure has an openboundary surface through which a substance may be transferred freelyfrom the inside of the structure to the outside thereof.

The conventional cable-type secondary batteries have an electrolytelayer which is interposed between an inner electrode and an outerelectrode. In order for the electrolyte layer to isolate the innerelectrode from the outer electrode and prevent a short circuit, theelectrolyte layer should be made of gel-type polymer electrolytes orsolid polymer electrolytes having a certain degree of mechanicalproperties. However, such gel-type polymer electrolytes or solid polymerelectrolytes fail to provide superior performances as a source forlithium ions, so an electrolyte layer made of such should have anincreased thickness so as to sufficiently provide lithium ions. Such athickness increase in the electrolyte layer widens an interval betweenthe electrodes to cause resistance increase, thereby deterioratingbattery performances. In contrast, as the cable-type secondary battery100 of the present invention has the core 110 for supplying lithiumions, which comprises an electrolyte, and the inner electrode 120 of thepresent invention has an open structure of inner current collector, theelectrolyte of the core 110 for supplying lithium ions can pass throughthe inner current collector to reach the inner electrode active materiallayer and the outer electrode active material layer 140. Accordingly, itis not necessary to excessively increase the thickness of an electrolytelayer. Also, an electrolyte layer may not be adopted as an essentialcomponent, and therefore, only a separator may be optionally used. Thus,the cable-type secondary battery of the present invention has the core110 for supplying lithium ions, which comprises an electrolyte, tofacilitate the penetration of an electrolyte into an electrode activematerial, and eventually facilitate the supply and exchange of lithiumions in electrodes, thereby exhibiting superior capacity and cyclecharacteristics.

The core 110 for supplying lithium ions comprises an electrolyte, andexamples of the electrolyte may include, but are not particularlylimited to, a non-aqueous electrolyte solution using ethylene carbonate(EC), propylene carbonate (PC), butylene carbonate (BC), vinylenecarbonate (VC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methyl formate (MF), γ-butyrolactone (γ-BL),sulfolane, methyl acetate (MA) or methyl propionate (MP); a gel polymerelectrolyte using PEO, PVdF, PVdF-HEP, PMMA, PAN, or PVAc; and a solidelectrolyte using PEO, polypropylene oxide (PPO), polyether imine (PEI),polyethylene sulphide (PES), or polyvinyl acetate (PVAc). Theelectrolyte further comprises a lithium salt, and the preferred examplesof the lithium salt include LiCl, LiBr, LiI, LiClO₄, LiBF₄, LaB₁₀Cl₁₀,LiPF₆, LiCF₃SO₃, LiCF₃CO₂, LiAsF₆, LiSbF₆, LiAlCl₄, CH₃SO₃Li, CF₃SO₃Li,(CF₃SO₂)₂NLi, lithium chloroborate, lower aliphatic lithium carbonate,lithium tetraphenylborate, and the like. Also, the core 110 forsupplying lithium ions may consist of only an electrolyte, and in thecase of a liquid electrolyte, a porous carrier may be used together.

The inner electrode 120 of the present invention has a spiral electrodeobtained by spirally twisting two or more wire-type current collectorscoated with an inner electrode active material on the surface thereof.

Referring to FIGS. 2 and 3, the spiral electrode 20 of the presentinvention is characterized by comprising at least two wire-typeelectrodes 21 which are arranged parallel to each other and spirallytwisted, each of the wire-type electrodes having a wire-type currentcollector 22 and an inner electrode active material layer 23 coated onthe surface of the wire-type current collector.

The spiral electrode 20 of the present invention is configured to haveseveral wire-type electrodes 21 being spirally twisted, and the twistingof the wire-type electrodes is not particularly limited. For example,the twisting may be carried out by placing several wire-type electrodes21 side by side to be parallel to each other and then twisting themtogether, or by intercrossing several wire-type electrodes 21 one afterthe other similar to long braided hair.

Generally, when the inner electrode is an anode, and a metal such as Siand Sn, or a compound containing such a metal, which is alloyed with Liions or dealloying due to its inherent properties to exhibitelectrochemical characteristics, is used as an anode material havinghigh capacity, there is a severely large volume change due to expansionwhich may cause the secondary battery to decay. This volume changeweakens the electronic contact between metal active materials, therebyinhibiting the transfer of Li ions into the anode active material layerto cause cycle deterioration. Also, if the anode active material layercomprises the metal in a high density and has a thick thickness, it isdifficult for Li ions to be diffused into the anode active materiallayer, thereby failing to provide sufficient capacity and good ratecharacteristics.

However, the spiral electrode 20 of the present invention consists ofseveral anodes 21 in which an anode active material 23 is coated on thesurface of a wire-type current collector 22, and the anodes are twistedtogether with each other and overlapped to increase a surface area forreaction with Li ions during a charging/discharging process, therebyimproving the performances of a battery. Also, since the anodes 21 havea thin anode active material layer, the rate characteristics of thebattery may be improved. In addition, the spiral electrode 20 has aspace present between the several strands of anodes, which can releasestress or pressure applied in the battery during a charging/dischargingprocess, e.g., the expansion of active material layers, to prevent thedeformation of the battery and ensure the stability thereof, therebyimproving the life cycle characteristic of the battery.

Preferably, the twist rate of the spiral electrode is in the range of0.01 to 10 mm per one twist. The twist rate is obtained by dividing thelength of the anode wire by the number of twists. The lower value thetwist rate has, the higher a twist degree is. When the twist rate isgreater than 10 mm per one twist, a contact area between wire-typeelectrodes 21 is so small that the increase of surface area isinsignificant. When the twist rate is lower than 0.01 mm per one twist,a twist degree becomes so excessive that it may damage the wire-typeelectrodes 21, such so that the inner electrode active material layermay be peeled off and the current collector may be ruptured.

The inner electrode having such a spiral electrode is configured in theform of an open structure so that the electrolyte comprised in the corefor supplying lithium ions can be easily penetrated, and any form whichallows the easy penetration of the electrolyte may be used as the openstructure. For example, the inner electrode having such an openstructure may be in the form of one spiral electrode 120 wound on theouter surface of the core 110 for supplying lithium ions, as shown inFIG. 1. Also, the inner electrode having such an open structure may bein the form of two or more spiral electrodes 220 wound on the outersurface of the core 210 for supplying lithium ions, as shown in FIG. 4,and these spiral electrodes may be wound in different directions fromeach other. In addition, the inner electrode having such an openstructure may be in the form of two or more spiral electrodes 320arranged parallel to each other in the longitudinal direction along theouter surface of the core for supplying lithium ions, as shown in FIG.5, and the spiral electrodes arranged parallel to each other may beintermittently intercrossed for the structural stability thereof.

The inner current collector 22 is preferably made of stainless steel,aluminum, nickel, titanium, sintered carbon, or copper; stainless steeltreated with carbon, nickel, titanium or silver on the surface thereof;an aluminum-cadmium alloy; a non-conductive polymer treated with aconductive material on the surface thereof; or a conductive polymer.

The current collector serves to collect electrons generated byelectrochemical reaction of the active material or to supply electronsrequired for the electrochemical reaction. In general, the currentcollector is made of a metal such as copper or aluminum. Especially,when the current collector is made of a non-conductive polymer treatedwith a conductive material on the surface thereof or a conductivepolymer, the current collector has a relatively higher flexibility thanthe current collector made of a metal such as copper or aluminum. Also,a polymer current collector may be used instead of the metal currentcollector to reduce the weight of the battery.

The conductive material may include polyacetylene, polyaniline,polypyrrole, polythiophene, polysulfurnitride, indium tin oxide (ITO),copper, silver, palladium, nickel, etc. The conductive polymer mayinclude polyacetylene, polyaniline, polypyrrole, polythiophene,polysulfurnitride, etc. However, the non-conductive polymer used for thecurrent collector is not particularly limited to its kinds.

In the present invention, the outer current collector is notparticularly limited to its forms, but is preferably in the form of apipe, a wound wire, a wound sheet or a mesh. The outer current collectormay be made of stainless steel, aluminum, nickel, titanium, sinteredcarbon, or copper; stainless steel treated with carbon, nickel, titaniumor silver on the surface thereof; an aluminum-cadmium alloy; anon-conductive polymer treated with a conductive material on the surfacethereof; a conductive polymer; a metal paste comprising metal powders ofNi, Al, Au, Ag, Al, Pd/Ag, Cr, Ta, Cu, Ba or ITO; or a carbon pastecomprising carbon powders of graphite, carbon black or carbon nanotube.

The inner electrode may be an anode and the outer electrode may be acathode. Alternatively, the inner electrode may be a cathode and theouter electrode may be an anode.

In the present invention, electrode active material layers allow ions tomove through the current collector, and the movement of ions is causedby the interaction of ions such as intercalation/deintercalation of ionsinto and from the electrolyte layer.

Such electrode active material layers may be divided into an anodeactive material layer and a cathode active material layer.

Specifically, when the inner electrode is an anode and the outerelectrode is a cathode, the inner electrode active material layerbecomes an anode active material layer and may be made of an activematerial selected from the group consisting of natural graphite,artificial graphite, or carbonaceous material; lithium-titanium complexoxide (LTO), and metals (Me) including Si, Sn, Li, Zn, Mg, Cd, Ce, Niand Fe; alloys of the metals; oxides (MeOx) of the metals; complexes ofthe metals and carbon; and mixtures thereof, and the outer electrodeactive material layer becomes a cathode active material layer and may bemade of an active material selected from the group consisting of LiCoO₂,LiNiO₂, LiMn₂O₄, LiCoPO₄, LiFePO₄, LiNiMnCoO₂,LiNi_(1-x-y-z)Co_(x)M1_(y)M2_(z)O₂ (wherein M1 and M2 are eachindependently selected from the group consisting of Al, Ni, Co, Fe, Mn,V, Cr, Ti, W, Ta, Mg and Mo, and x, y and z are each independently anatomic fraction of oxide-forming elements, in which 0≦x<0.5, 0≦y<0.5,0≦z<0.5, and x+y+z≦1), and mixtures thereof.

Alternatively, when the inner electrode is a cathode and the outerelectrode is an anode, the inner electrode active material layer becomesa cathode active material layer and the outer electrode active materiallayer becomes an anode active material layer.

As mentioned above, referring to FIG. 1, the outer electrode comprisesan outer electrode active material layer 140 surrounding the outersurface of the separation layer 130 and an outer current collector 150surrounding the outer surface of the outer electrode active materiallayer 140.

Also, the outer electrode may have the outer current collector formed tosurround the outer surface of the separation layer, and the outerelectrode active material layer formed to surround the outer surface ofthe outer current collector; or the outer current collector formed tosurround the outer surface of the separation layer, and the outerelectrode active material layer formed to surround the outer surface ofthe outer current collector and to come into contact with the separationlayer; or the outer electrode active material layer formed to surroundthe outer surface of the separation layer, and the outer currentcollector formed to be included inside the outer electrode activematerial layer by being covered therein and to surround the outersurface of the separation layer with spacing apart therefrom.

Specifically, if the outer current collector is wound on the outersurface of the separation layer, a contact area of the separation layerand the active material layer sufficiently increases to ensure a certaindegree of battery performances. Particularly, since the outer electrodeactive material layer of the present invention is formed by coating anactive material in the form of a slurry on the outer surface of theouter current collector, the outer electrode active material layer comesinto contact with the separation layer. Also, the outer currentcollector is included inside the outer electrode active material layerby being covered therein, while surrounding the outer surface of theseparation layer with spacing apart therefrom by the outer electrodeactive material layer. As a result, an electric contact between theouter current collector and the outer electrode active material layer isimproved, thereby contributing to the enhancement of batterycharacteristics.

For example, when the outer current collector is in the form of a woundwire having flexibility, the wound wire-form outer current collector haselasticity due to its form to enhance the overall flexibility of thecable-type secondary battery. Also, when excessive external force isapplied to the cable-type secondary battery of the present invention,the wire-form outer current collector of the present invention undergoesvery little excessive deformation such as crumpling or bending, so ashort circuit due to a contact with an inner current collector may beavoided.

The electrode active material layer comprises an electrode activematerial, a binder and a conductive material, and is combined with acurrent collector to configure an electrode. If the electrode isdeformed by bending or severe folding due to external force, theelectrode active material may be released. The release of the electrodeactive material deteriorates the performance and capacity of batteries.However, in accordance with the present invention, since the woundwire-form outer current collector has elasticity, it can disperse theapplied force when such a deformation occurs by the external force,which causes only a slight deformation of the active material layer,thereby preventing the release of the active material.

The separation layer of the present invention may be an electrolytelayer or a separator.

The electrolyte layer serving as an ion channel may be made of agel-type polymer electrolyte using PEO, PVdF, PVdF-HFP, PMMA, PAN orPVAC, or a solid electrolyte using PEO, polypropylene oxide (PPO),polyethylene imine (PEI), polyethylene sulfide (PES) or polyvinylacetate (PVAc). The matrix of the solid electrolyte is preferably formedusing a polymer or a ceramic glass as the backbone. In the case of thetypical polymer electrolytes, the ions move very slowly in terms ofreaction rate, even when the ionic conductivity is satisfied. Thus, thegel-type polymer electrolyte which facilitates the movement of ions ispreferably used compared to the solid electrolyte. The gel-type polymerelectrolyte has poor mechanical properties and thus may comprise aporous support or a cross-linked polymer to improve the poor mechanicalproperties. The electrolyte layer of the present invention can serve asa separator, and thus an additional separator may be omitted.

The electrolyte layer of the present invention may further comprise alithium salt. The lithium salt can improve an ionic conductivity andresponse time. Non-limiting examples of the lithium salt may includeLiCl, LiBr, LiI, LiClO₄, LiBF₄, LiB₁₀Cl₁₀, LiPF₆, LiCF₃SO₃, LiCF₃CO₂,LiAsF₆, LiSbF₆, LiAlCl₄, CH₃SO₃Li, CF₃SO₃Li, (CF₃SO₂)₂NLi, lithiumchloroborate, lower aliphatic lithium carbonate, and lithiumtetraphenylborate.

Examples of the separator may include, but is not limited to, a poroussubstrate made of a polyolefin-based polymer selected from the groupconsisting of ethylene homopolymers, propylene homopolymers,ethylene-butene copolymers, ethylene-hexene copolymers, andethylene-methacrylate copolymers; a porous substrate made of a polymerselected from the group consisting of polyesters, polyacetals,polyamides, polycarbonates, polyimides, polyether ether ketones,polyether sulfones, polyphenylene oxides, polyphenylene sulfides andpolyethylene naphthalenes; or a porous substrate made of a mixture ofinorganic particles and a binder polymer. Among these, in order for thelithium ions of the core for supplying lithium ions to be transferred tothe outer electrode, it is preferred to use a non-woven fabric separatorcorresponding to the porous substrate made of a polymer selected fromthe group consisting of polyesters, polyacetals, polyamides,polycarbonates, polyimides, polyether ether ketones, polyether sulfones,polyphenylene oxides, polyphenylene sulfides and polyethylenenaphthalenes.

Also, the cable-type secondary battery of the present invention has aprotection coating. The protection coating is an insulator and is formedto surround the outer current collector, thereby protecting theelectrodes against moisture in the air and external impacts. Theprotection coating may be made of conventional polymer resins, forexample, PVC, HDPE or epoxy resins.

Hereinafter, a cable-type secondary battery according to one embodimentof the present invention and the manufacture thereof will be brieflyexplained with reference to FIG. 1.

A cable-type secondary battery 100 according to one embodiment of thepresent invention comprises a core 110 for supplying lithium ions, whichcomprises an electrolyte; an inner electrode 120, surrounding the outersurface of the core 110 for supplying lithium ions, and comprising aspiral electrode formed by spirally twisting two or more wire-typecurrent collectors coated with an inner electrode active material on thesurface thereof; a separation layer 130 surrounding the outer surface ofthe inner electrode to prevent a short circuit between electrodes; andan outer electrode comprising an outer electrode active material layer140 surrounding the outer surface of the separation layer and an outercurrent collector 150 surrounding the outer surface of the outerelectrode active material layer 140.

First, a polymer electrolyte is provided in the form of a wire using anextruder to prepare the core 110 for supplying lithium ions. Also, thecore 110 for supplying lithium ions may be formed by providing a hollowinner electrode and introducing a non-aqueous electrolyte solution inthe center of the inner electrode, or by providing a battery assemblycomprising a protection coating as well as the others and introducing anon-aqueous electrolyte solution in the center of the inner electrodesupport comprised in the battery assembly. Alternatively, the core 110for supplying lithium ions may be prepared by providing a wire-formcarrier made of a sponge material and introducing a non-aqueouselectrolyte solution thereto.

Then, a linear wire-type inner current collector is provided, and aninner electrode active material layer is formed by way of coating on thesurface of the wire-type inner current collector to prepare a wire-typeelectrode. The coating may be carried out by various conventionalmethods, for example, by an electroplating process or an anodicoxidation process. Also, in order to maintain constant intervals, anelectrode slurry containing an active material may be discontinuouslyapplied by way of an extrusion-coating using an extruder. In addition,the electrode slurry containing an active material may be applied by wayof dip coating or extrusion-coating using an extruder. The wire-typeelectrode thus prepared is provided in several strands and spirallytwisted with each other to obtain a spiral electrode, and then thespiral electrode is wound on the outer surface of the core 110 forsupplying lithium ions to form the inner electrode 120.

Subsequently, the separation layer 130 consisting of a polymerelectrolyte layer is formed to surround the inner electrode 120. Theseparation layer 130 which is an electrolyte layer may be formed byvarious methods, for example, by way of extrusion-coating consideringthe linear structure of the cable-type secondary battery.

On the outer surface of the separation layer 130 formed by the coatingof an electrolyte, the outer electrode active material layer 140 isformed by way of coating. The coating method of the inner electrodeactive material layer may be identically applied to the outer electrodeactive material layer 140.

Then, an outer current collector in the form of a wire is provided andwound on the outer surface of the outer electrode active material layer140 to form the wound wire-type outer current collector 150. As theouter current collector, a wound sheet-, pipe- or mesh-form currentcollector may also be used. At this time, the outer electrode activematerial layer may be first formed on the outer current collector andthen the separation layer is applied thereon, to form the outerelectrode. For example, in the case of the wound sheet-form currentcollector, the outer electrode active material layer may be first formedon the wound sheet-form current collector, followed by cutting into apiece having a predetermined size, to prepare a sheet-form outerelectrode. Then, the prepared sheet-form outer electrode may be wound onthe outer surface of the separation layer so that the outer electrodeactive material layer comes into contact with the separation layer, toform the outer electrode on the separation layer.

As another method, in the formation of the outer electrode, the outercurrent collector may be first formed to surround the outer surface ofthe separation layer, and then followed by forming the outer electrodeactive material layer to surround the outer surface of the outer currentcollector.

Meanwhile, in the case of a structure having the outer current collectorformed to surround the outer surface of the separation layer, and theouter electrode active material layer formed to surround the outersurface of the outer current collector and to come into contact with theseparation layer, first, an outer current collector, for example, in theform of a wire or sheet, is wound on the outer surface of the separationlayer. The winding method is not particularly limited. For example, inthe case of the wire-form current collector, the winding may be carriedout by using a winding machine on the outer surface of the separationlayer. Then, the outer electrode active material layer is formed by wayof coating on the outer surface of the wound wire- or sheet-form outercurrent collector so that the outer electrode active material layersurrounds the outer current collector and comes into contact with theseparation layer.

Also, in the case of a structure having the outer electrode activematerial layer formed to surround the outer surface of the separationlayer, and the outer current collector formed to be included inside theouter electrode active material layer by being covered therein and tosurround the outer surface of the separation layer with spacing aparttherefrom, first, on the outer surface of the separation layer, a partof the outer electrode active material layer to be finally obtained isformed, on which the outer current collector is formed to surround thepart of the outer electrode active material layer, and then the outerelectrode active material layer is further formed on the outer currentcollector to completely cover the outer current collector. Thereby, theouter current collector is disposed inside the outer electrode activematerial layer to improve an electric contact between the currentcollector and the active material, thereby enhancing batterycharacteristics.

Finally, the protection coating 160 is formed to surround the outersurface of the electrode assembly. The protection coating 160 is aninsulator and is formed on the outermost surface for the purpose ofprotecting the electrodes against moisture in the air and externalimpacts. As the protection coating 160, conventional polymer resins, forexample, PVC, HDPE and epoxy resins may be used.

Hereinafter, other embodiments of the present invention will be brieflyexplained with reference to FIGS. 4, 5 and 6.

Referring to FIG. 4, a cable-type secondary battery 200 according to oneembodiment of the present invention comprises a core 210 for supplyinglithium ions, which comprises an electrolyte; an inner electrode 220surrounding the outer surface of the core for supplying lithium ions,and comprising two spiral electrodes formed by spirally twisting two ormore wire-type current collectors coated with an inner electrode activematerial on the surface thereof, wherein the spiral electrodes are woundon the outer surface of the core for supplying lithium ions; aseparation layer 230 surrounding the outer surface of the innerelectrode 220 to prevent a short circuit between electrodes; and anouter electrode comprising an outer electrode active material layer 240surrounding the outer surface of the separation layer 230 and an outercurrent collector 250 surrounding the outer surface of the outerelectrode active material layer 240.

Referring to FIG. 5, a cable-type secondary battery 300 according to oneembodiment of the present invention comprises a core 310 for supplyinglithium ions, which comprises an electrolyte; an inner electrode 320surrounding the outer surface of the core for supplying lithium ions,and comprising two spiral electrodes formed by spirally twisting two ormore wire-type current collectors coated with an inner electrode activematerial on the surface thereof, wherein the spiral electrodes arearranged parallel to each other in the longitudinal direction along theouter surface of the core for supplying lithium ions; a separation layer330 surrounding the outer surface of the inner electrode 320 to preventa short circuit between electrodes; and an outer electrode comprising anouter electrode active material layer 340 surrounding the outer surfaceof the separation layer 330 and an outer current collector 350surrounding the outer surface of the outer electrode active materiallayer 340.

Referring to FIG. 6, a cable-type secondary battery 400 according to oneembodiment of the present invention comprises two or more cores 410 forsupplying lithium ions, which comprise an electrolyte; two or more innerelectrodes 420 arranged parallel to each other, each inner electrodesurrounding the outer surface of each core 410 for supplying lithiumions, and comprising a spiral electrode formed by spirally twisting twoor more wire-type current collectors coated with an inner electrodeactive material on the surface thereof; a separation layer 430surrounding the outer surface of the inner electrodes 420 to prevent ashort circuit between electrodes; and an outer electrode comprising anouter electrode active material layer 440 surrounding the outer surfaceof the separation layer 430 and an outer current collector 450surrounding the outer surface of the outer electrode active materiallayer 440. Such a cable-type secondary battery 400 has the innerelectrode consisting of multiple electrodes, thereby allowing to controlthe balance between a cathode and anode and prevent a short circuit.

Also, in the cable-type secondary batteries of FIGS. 4 to 6, besides thestructure of the outer electrode having the outer electrode activematerial layer formed to surround the outer surface of the separationlayer, and the outer current collector formed to surround the outersurface of the outer electrode active material layer, as mentionedabove, the outer electrode may be formed in a structure having the outercurrent collector formed to surround the outer surface of the separationlayer, and the outer electrode active material layer formed to surroundthe outer surface of the outer current collector; a structure having theouter current collector formed to surround the outer surface of theseparation layer, and the outer electrode active material layer formedto surround the outer surface of the outer current collector and to comeinto contact with the separation layer; or a structure having the outerelectrode active material layer formed to surround the outer surface ofthe separation layer, and the outer current collector formed to beincluded inside the outer electrode active material layer by beingcovered therein and to surround the outer surface of the separationlayer with spacing apart therefrom.

<Explanation of Reference Numerals> 20: Spiral Electrode 21: Wire-typeInner Electrode 22: Wire-type Inner Current 23: Inner Electrode ActiveMaterial Collector Layer 100, 200, 300, 400: Cable-type SecondaryBattery 110, 210, 310, 410: Core for Supplying Lithium Ions 120, 220,320, 420: Inner Electrode 130, 230, 330, 430: Separation Layer 140, 240,340, 440: Outer Electrode Active Material Layer 150, 250, 350, 450:Outer Current Collector 160, 260, 360, 460: Protection Coating

What is claimed is:
 1. A cable-type secondary battery having ahorizontal cross section of a predetermined shape and extendinglongitudinally, comprising: a core for supplying lithium ions, whichcomprises an electrolyte; an inner electrode, comprising a spiralelectrode formed by spirally twisting two or more wire-type innercurrent collectors coated with an inner electrode active material on thesurface thereof a separation layer surrounding the outer surface of theinner electrode to prevent a short circuit between electrodes; and anouter electrode surrounding the outer surface of the separation layer,and comprising an outer electrode active material layer and an outercurrent collector.
 2. The cable-type secondary battery according toclaim 1, wherein the inner electrode comprises one or more spiralelectrodes to be wound to surround the outer surface the core forsupplying lithium ions.
 3. The cable-type secondary battery according toclaim 1, wherein the inner electrode comprises one or more spiralelectrodes arranged parallel to each other in the longitudinal directionalong the outer surface of the core for supplying lithium ions.
 4. Thecable-type secondary battery according to claim 1, wherein in the outerelectrode, the outer electrode active material layer is formed tosurround the outer surface of the separation layer, and the outercurrent collector is formed to surround the outer surface of the outerelectrode active material layer; the outer current collector is formedto surround the outer surface of the separation layer, and the outerelectrode active material layer is formed to surround the outer surfaceof the outer current collector; the outer current collector is formed tosurround the outer surface of the separation layer, and the outerelectrode active material layer is formed to surround the outer surfaceof the outer current collector and come into contact with the separationlayer; or the outer electrode active material layer is formed tosurround the outer surface of the separation layer, and the outercurrent collector is formed to be included inside the outer electrodeactive material layer by being covered therein and to surround the outersurface of the separation layer with spacing apart therefrom.
 5. Thecable-type secondary battery according to claim 1, wherein the outercurrent collector is in the form of a pipe, a wound wire, a wound sheetor a mesh.
 6. The cable-type secondary battery according to claim 1,wherein the inner current collector is made of stainless steel,aluminum, nickel, titanium, sintered carbon, or copper; stainless steeltreated with carbon, nickel, titanium or silver on the surface thereof;an aluminum-cadmium alloy; a non-conductive polymer treated with aconductive material on the surface thereof; or a conductive polymer. 7.The cable-type secondary battery according to claim 6, wherein theconductive material is selected from the group consisting ofpolyacetylene, polyaniline, polypyrrole, polythiophene,polysulfurnitride, indium tin oxide (ITO), silver, palladium, nickel,and mixtures thereof.
 8. The cable-type secondary battery according toclaim 6, wherein the conductive polymer is selected from the groupconsisting of polyacetylene, polyaniline, polypyrrole, polythiophene,polysulfurnitride, and mixtures thereof.
 9. The cable-type secondarybattery according to claim 1, wherein the outer current collector ismade of stainless steel, aluminum, nickel, titanium, sintered carbon, orcopper; stainless steel treated with carbon, nickel, titanium or silveron the surface thereof; an aluminum-cadmium alloy; a non-conductivepolymer treated with a conductive material on the surface thereof; aconductive polymer; a metal paste comprising metal powders of Ni, Al,Au, Ag, Al, Pd/Ag, Cr, Ta, Cu, Ba or ITO; or a carbon paste comprisingcarbon powders of graphite, carbon black or carbon nanotube.
 10. Thecable-type secondary battery according to claim 1, wherein theelectrolyte comprises an electrolyte selected from a non-aqueouselectrolyte solution using ethylene carbonate (EC), propylene carbonate(PC), butylene carbonate (BC), vinylene carbonate (VC), diethylcarbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC),methyl formate (MF), γ-butyrolactone (γ-BL), sulfolane, methyl acetate(MA) or methyl propionate (MP); a gel polymer electrolyte using PEO,PVdF, PVdF-HEP, PMMA, PAN, or PVAc; and a solid electrolyte using PEO,polypropylene oxide (PPO), polyether imine (PEI), polyethylene sulphide(PES), or polyvinyl acetate (PVAc).
 11. The cable-type secondary batteryaccording to claim 1, wherein the electrolyte further comprises alithium salt.
 12. The cable-type secondary battery according to claim11, wherein the lithium salt is selected from the group consisting ofLiCl, LiBr, LiI, LiClO₄, LiBF₄, LiB₁₀Cl₁₀, LiPF₆, LiCF₃SO₃, LiCF₃CO₂,LiAsF₆, LiSbF₆, LiAlCl₄, CH₃SO₃Li, CF₃SO₃Li, (CF₃SO₂)₂NLi, lithiumchloroborate, lower aliphatic lithium carbonate, lithiumtetraphenylborate, and mixtures thereof.
 13. The cable-type secondarybattery according to claim 1, wherein the inner electrode is an anodeand the outer electrode is a cathode, or the inner electrode is acathode and the outer electrode is an anode.
 14. The cable-typesecondary battery according to claim 1, wherein when the inner electrodeis an anode and the outer electrode is a cathode, the inner electrodeactive material layer comprises an active material selected from thegroup consisting of natural graphite, artificial graphite, orcarbonaceous material; lithium-titanium complex oxide (LTO), and metals(Me) including Si, Sn, Li, Zn, Mg, Cd, Ce, Ni and Fe; alloys of themetals; oxides (MeOx) of the metals; complexes of the metals and carbon;and mixtures thereof, and the outer electrode active material layercomprises an active material selected from the group consisting ofLiCoO₂, LiNiO₂, LiMn₂O₄, LiCoPO₄, LiFePO₄, LiNiMnCoO₂,LiNi_(1-x-y-z)Co_(x)M1_(y)M2_(z)O₂ (wherein M1 and M2 are eachindependently selected from the group consisting of Al, Ni, Co, Fe, Mn,V, Cr, Ti, W, Ta, Mg and Mo, and x, y and z are each independently anatomic fraction of oxide-forming elements, in which 0≦x<0.5, 0≦y<0.5,0≦z<0.5, and x+y+z≦1), and mixtures thereof.
 15. The cable-typesecondary battery according to claim 1, wherein when the inner electrodeis a cathode and the outer electrode is an anode, the inner electrodeactive material layer comprises an active material selected from thegroup consisting of LiCoO₂, LiNiO₂, LiMn₂O₄, LiCoPO₄, LiFePO₄,LiNiMnCoO₂, LiNi_(1-x-y-z)Co_(x)M1_(y)M2_(z)O₂ (wherein M1 and M2 areeach independently selected from the group consisting of Al, Ni, Co, Fe,Mn, V, Cr, Ti, W, Ta, Mg and Mo, and x, y and z are each independentlyan atomic fraction of oxide-forming elements, in which 0≦x<0.5, 0≦y<0.5,0≦z<0.5, and x+y+z≦1), and mixtures thereof, and the outer electrodeactive material layer comprises an active material selected from thegroup consisting of natural graphite, artificial graphite, orcarbonaceous material; lithium-titanium complex oxide (LTO), and metals(Me) including Si, Sn, Li, Zn, Mg, Cd, Ce, Ni and Fe; alloys of themetals; oxides (MeOx) of the metals; complexes of the metals and carbon;and mixtures thereof.
 16. The cable-type secondary battery according toclaim 1, wherein the separation layer is an electrolyte layer or aseparator.
 17. The cable-type secondary battery according to claim 16,wherein the electrolyte layer comprises an electrolyte selected from agel polymer electrolyte using PEO, PVdF, PVdF-HFP, PMMA, PAN, or PVAc;and a solid electrolyte using PEO, polypropylene oxide (PPO), polyetherimine (PEI), polyethylene sulphide (PES), or polyvinyl acetate (PVAc).18. The cable-type secondary battery according to claim 16, wherein theelectrolyte layer further comprises a lithium salt.
 19. The cable-typesecondary battery according to claim 18, wherein the lithium salt isselected from the group consisting of LiCl, LiBr, LiI, LiClO₄, LiBF₄,LiB₁₀Cl₁₀, LiPF₆, LiCF₃SO₃, LiCF₃CO₂, LiAsF₆, LiSbF₆, LiAlCl₄, CH₃SO₃Li,CF₃SO₃Li, (CF₃SO₂)₂NLi, lithium chloroborate, lower aliphatic lithiumcarbonate, lithium tetraphenylborate, and mixtures thereof.
 20. Thecable-type secondary battery according to claim 16, wherein theseparator is a porous substrate made of a polyolefin-based polymerselected from the group consisting of ethylene homopolymers, propylenehomopolymers, ethylene-butene copolymers, ethylene-hexene copolymers,and ethylene-methacrylate copolymers; a porous substrate made of apolymer selected from the group consisting of polyesters, polyacetals,polyamides, polycarbonates, polyimides, polyether ether ketones,polyether sulfones, polyphenylene oxides, polyphenylene sulfides andpolyethylene naphthalenes; or a porous substrate made of a mixture ofinorganic particles and a binder polymer.
 21. A cable-type secondarybattery having a horizontal cross section of a predetermined shape andextending longitudinally, comprising: two or more cores for supplyinglithium ions, which comprises an electrolyte; two or more innerelectrodes arranged parallel to each other, each inner electrodecomprising a spiral electrode formed by spirally twisting two or morewire-type inner current collectors coated with an inner electrode activematerial on the surface thereof; a separation layer surrounding theouter surface of the inner electrode to prevent a short circuit betweenelectrodes; and an outer electrode surrounding the outer surface of theseparation layer, and comprising an outer electrode active materiallayer and an outer current collector.
 22. A cable-type secondary batteryaccording to claim 21, wherein the inner electrodes each comprise one ormore spiral electrodes to be wound to surround the outer surface of thecore for supplying lithium ions.
 23. A cable-type secondary batteryaccording to claim 21, wherein the inner electrodes each comprise one ormore spiral electrodes arranged parallel to each other in thelongitudinal direction along the outer surface of the core for supplyinglithium ions.